Integrated circuits with a minimalist design in relation to the power consumption thereof are known. The origin of this trend is the extensive growth of those applications in which energy consumption is crucial, such as RFID (Radio Frequency Identification) transponders, wireless sensors, etc.
Most of these circuits have a battery with a very limited energy capacity (active circuits) and the rest of the circuits collect and temporarily store the energy from a radiant source for the correct operation thereof (passive circuits).
Therefore in both of the circuits it is desirable to have low power consumption.
Patent application US 2005/0135456 A1 describes a radio frequency temperature sensor comprising an oscillator generating a signal the frequency of which depends on the temperature. This is achieved through the delay caused by a thermal resistor and a capacitor.
However, the temperature sensor described in US 2005/0135456 A1 has a series of drawbacks, such as the need for a large amount of surface area to integrate the RC (resistor and capacitor) resonant tank, as well as the difficulty of adapting this core (RC) according to the desired temperature variation range.